Ophthalmologic photographing apparatus

ABSTRACT

When an observation state by an infrared LED  10  is changed to a photographing state by a xenon lamp  3,  a movable mirror  16  is pulled upward and an optical path is switched to an image sensor  17  side. A light guide  22   a  is shifted by an alignment index drive motor  23  so that an incident portion of an alignment index is shifted from a visible LED  22   b  to direct to an infrared LED  22   c.  An outgoing portion of the light guide  22   a  is set at a position where an image is formed on the image sensor  17  by a wavelength of the infrared LED  22   c  when an operation distance is appropriate. While changing a luminescent color, a position of a luminescent point of the alignment index is changed by switching the LED by the shift of the light guide  22   a.

TECHNICAL FIELD

The present invention relates to an ocular fundus observation apparatuswhich can change an observation light source between infrared light andvisible light to perform observation.

BACKGROUND ART

In recent years, a mydriatic/non-mydriatic combination type funduscamera has been used in an ocular fundus observation apparatus,particularly in a fundus camera, to reduce a burden of a subject as muchas possible. The mydriatic/non-mydriatic combination type fundus cameracan perform mydriatic photographing and non-mydriatic photographingcorresponding to contents of examination by one fundus camera.

Generally, infrared light is used in observation before non-mydriaticphotographing, and visible light is used in observation before mydriaticphotographing. In Japanese Patent Application Laid-Open No. 7-100112, itis discussed that visible light and infrared light are selectively usedas an observation light source of an eye to be examined and a wavelengthof an alignment index projection light source is changed correspondingto the observation light source, thereby improving visibility of analignment index.

In Japanese Patent Application Laid-Open No. 2003-305009, a funduscamera is discussed which selectively uses visible light and infraredlight as a light source of observation of an eye to be examined and usesnear infrared light as an alignment light source. This fundus cameraimproves visibility of an alignment index by increasing a quantity oflight of the alignment light source in case of visible light observationmore than that in case of infrared light observation.

In Japanese Patent Application Laid-Open No. 2000-287934, a position forprojecting an alignment index is shifted in a direction of an opticalaxis in case of photographing a center of an ocular fundus of an eye tobe examined and in case of photographing the periphery thereof, therebysuppressing occurrence of flare.

However, as discussed in Japanese Patent Application Laid-Open No.7-100112, when a wavelength of an alignment index projection lightsource is changed, a focus is changed with a difference between thewavelengths and an alignment index is deviated there from. Thus, itbecomes difficult to obtain correct focus.

Further, a method discussed in Japanese Patent Application Laid-Open No.2003-305009 in which an alignment index is provided by near infraredlight and the luminance thereof is changed corresponding to anobservation wavelength, is needed to enhance the intensity of light ofless-visible wavelength in visible light observation. Even if thismethod can be recognized by an examiner, visibility is hardly excellentfor a subject.

A method discussed in Japanese Patent Application Laid-Open No.2000-287934 in which the position for projecting the alignment index isshifted to suppress occurrence of flare is not devised a measure toimprove the visibility when the characteristic of the observation lightsource is changed.

CITATION LIST Patent Literature

PTL 1: Japanese Patent Application Laid-Open No. 7-100112

PTL 2: Japanese Patent Application Laid-Open No. 2003-305009

PTL 3: Japanese Patent Application Laid-Open No. 2000-287934

SUMMARY OF INVENTION

The present invention is directed to an ocular fundus observationapparatus which can select a color of an alignment index which isexcellent in visibility to an observation light source when theobservation light source is changed and can obtain a suitable focalstate to the selected color.

According to an aspect of the present invention, an ocular fundusobservation apparatus includes an illumination optical system configuredto illuminate an ocular fundus of an eye to be examined, an observationphotographing optical system configured to observe and photograph theocular fundus illuminated by the illumination optical system, analignment index unit which is configured to project an alignment indexon an anterior eye portion of the eye to be examined in order to adjusta position relation between the observation photographing optical systemand the eye to be examined, and is disposed to cause an image of aluminescent spot of the alignment index to be formed when an alignmentis aligned with the anterior eye portion by shifting the observationphotographing optical system, an infrared index light source configuredto emit near infrared light and a visible index light source configuredto emit visible light which are provided on the alignment index unit, anindex light source change unit configured to change these index lightsources, an index projection unit configured to cause the index lightsource to emit light, and a shift control unit configured to control aposition of the index projection unit in a direction of an optical axis,wherein a position of the luminescent spot of the index projection unitis changed by the shift control unit according to selection of the indexlight source of the index light source change unit.

Other features and advantages of the present invention will be apparentfrom the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate exemplary embodiments, features,and aspects of the invention and, together with the description, serveto explain the principles of the invention.

FIG. 1 is a block diagram illustrating a fundus camera according to afirst exemplary embodiment.

FIG. 2A is a development elevation illustrating a split optical system.

FIG. 2B is a development elevation illustrating a split optical system.

FIG. 3 illustrates an optical path diagram when an alignment index isprojected by visible light.

FIG. 4 illustrates an optical path diagram when a light source ischanged from visible light to infrared light without adjusting aposition of an alignment index.

FIG. 5 illustrates an optical path diagram when a light source ischanged from visible light to infrared light by adjusting a position ofan alignment index.

FIG. 6 illustrates a block circuit diagram.

FIG. 7 is a flowchart illustrating an operation for changing a color anda position of an alignment index.

FIG. 8 illustrates a block diagram according to a second exemplaryembodiment.

DESCRIPTION OF EMBODIMENTS

Various exemplary embodiments, features, and aspects of the inventionwill be described in detail below with reference to the drawings.

FIG. 1 is a block diagram illustrating a fundus camera according to afirst exemplary embodiment. In an illumination optical system from ahalogen lamp 1 to an objective lens 2 disposed in front of an eye to beexamined E, the halogen lamp 1 as an observation light source, a xenonlamp 3 as a photographing light source, a visible light ring slit 4, anda dichroic mirror 5 are arranged on an optical path L1. Further, on anoptical path L2 on the reflection side of the dichroic mirror 5, a relaylens 6, a prism unit 7, a relay lens 8, and a perforated mirror 9 arearranged. Furthermore, in a direction coaxial with the optical path L2in the rear of the dichroic mirror 5, an infrared light emitting diode(LED) 10 as an observation light source and an infrared ring slit 11 areprovided.

The halogen lamp 1 is a first observation light source of visible lightto be used when an ocular fundus Er of the eye to be examined E isobserved by visible light. The xenon lamp 3 is the photographing lightsource to be used when the ocular fundus Er is photographed by visiblelight. The infrared LED 10 is a second observation light source to beused when the ocular fundus Er is observed by infrared light. Thevisible light ring slit 4 is a mask for subjecting illumination lightfrom the xenon lamp 3 and the halogen lamp 1 to ring illumination. Theinfrared ring slit 11 is a mask for subjecting illumination light fromthe infrared LED 10 to ring illumination. The dichroic mirror 5 hascharacteristics for reflecting visible light and transmitting infraredlight.

The prism unit 7 is provided with a split mask 7 a on the optical pathL2 and a split prism 7 b is attached in the rear of the split mask 7 a.A dichroic mirror 7 c is disposed in a direction of reflection on thesplit prism 7 b. A visible LED 7 d is disposed in a direction oftransmission to the dichroic mirror 7 c. A near infrared LED 7 e isdisposed in a direction of reflection on the dichroic mirror 7 c. Asplit drive motor 12 and a split position detection unit 13 are providedon the prism unit 7 to drive the prism unit 7, so that a split image onthe ocular fundus Er is shifted and a position thereof can be detected.

On an optical path L3 in the front of the eye to be examined E, theobjective lens 2, the perforated mirror 9, a diaphragm 14, a focus lens15, a movable mirror 16, and an image sensor 17 are arranged in thisorder. Thus, an observation photographing optical system is configured.On the focus lens 15, a focus lens drive motor 18 and a focus lensposition detection unit 19 are attached to drive the focus lens 15, sothat the focus lens 15 can come into focus and be detected the positionthereof.

On an optical path L4 in a direction of reflection on the movable mirror16, a fixed mirror 20 and a finder eyepiece lens 21 are arranged. Thus,a visible light observation optical system is configured.

In the hole of the perforated mirror 9, a light guide 22 a of analignment index unit 22 is disposed for adjusting a position relationbetween the observation photographing optical system and the eye to beexamined E. The alignment index unit 22 includes the light guide 22 adirected to the eye to be examined E, and a visible LED 22 b foremitting visible light and an infrared LED 22 c for emitting infraredlight which are provided in the vicinity of the incident portion of thelight guide 22 a. The visible LED 22 b and the infrared LED 22 c aredisposed side by side in a direction of an optical axis. The incidentportion of the light guide 22 a is directed in a direction orthogonal tothe optical axis. Further, for the alignment index unit 22, an alignmentindex drive motor 23 and an alignment index position detection unit 24which serve as a shift control unit and an index light source changeunit of the alignment index unit 22 are provided.

For the fundus camera, a focus adjustment knob 25, a focus adjustmentdetection unit 26, and an observation light source selection switch 27are provided. The observation light source selection switch 27 allows anexaminer to alternatively select visible/infrared light from the halogenlamp 1 and the infrared LED

When the ocular fundus of the eye to be examined E is observed, visiblelight emitted from the halogen lamp 1 passes through the xenon lamp 3and the visible light ring slit 4, and is reflected by the dichroicmirror 5. The visible light reflected by the dichroic mirror 5 passesthrough the relay lens 6, the prism unit 7, and the relay lens 8, isreflected by the perforated mirror 9, and is incident on the eye to beexamined E via the objective lens 2.

When the ocular fundus is observed, infrared light emitted from theinfrared LED 10 transmits the infrared ring slit 11 and the dichroicmirror 5, then passes through an optical path similar to theillumination light from the halogen lamp 1, and is incident on the eyeto be examined E. At this time, the optical paths of visible light ringillumination light and infrared light ring illumination light areintegrated by the dichroic mirror 5, and the ring illumination issubjected to image formation on the ocular fundus Er of the eye to beexamined E by the relay lenses 6 and 8.

An ocular fundus image obtained by the illumination is formed at aposition of the diaphragm 14 in the vicinity of the perforated mirror 9by the objective lens 2 and further travels through the observationphotographing optical system. The focus lens 15 is shifted in adirection indicated by an arrow in FIG. 1 by an operation of the focusadjustment knob 25, so that focus adjustment to photographing lightpassing through the perforated mirror 9 is performed. The focusadjustment knob 25 can be operated by the examiner to adjust to adesired focus state and the position thereof is detected by the focusadjustment detection unit 26.

The movable mirror 16 descends in observation by visible light asillustrated in FIG. 1, to introduce the ocular fundus image into thefinder eyepiece lens 21 via the fixed mirror 20 on the visible lightobservation optical system, so that the examiner can observe the ocularfundus image via the finder eyepiece lens 21. The movable mirror 16ascends during infrared observation and photographing to introducephotographing light into the image sensor 17 on the observationphotographing optical system. The image sensor 17 performs photoelectricconversion of the photographing light. An obtained electric signal issubjected to analog-to-digital (A/D) conversion by a processing circuit.The photographed image is displayed by a display unit (not illustrated)during infrared observation and recorded on a recording medium duringphotographing.

FIGS. 2A and 2B are development elevations illustrating a split opticalsystem according to the first exemplary embodiment. A reflection surfaceof the split prism 7 b and a reflection surface of the perforated mirror9 are omitted from drawing. The optical system is developed andillustrated. As illustrated in FIG. 2A, a luminous flux when the visibleLED 7 d is turned on transmits the dichroic mirror 7 c and is split bythe split prism 7 b. A split image results in a straight-line image bythe split mask 7 a disposed in a close position to the split prism 7 b.Accordingly, the image is formed on the perforated mirror 9 by the relaylens 8, and two split images are projected on the ocular fundus Er bythe objective lens 2 in a state of a straight line similarly when thesplit visible LED is emitted.

As illustrated in FIG. 2B, when the visible LED 7 d to be turned on inthis state is changed to the near infrared LED 7 e, a change in opticalpath length occurs by chromatic aberration due to a difference in colorof the LEDs. When the near infrared LED 7 e is turned on, a luminousflux thereof is reflected by the dichroic mirror 7 c and then travelsthe similar light path to the visible LED 7 d. However, because theoptical path length is elongated by the chromatic aberration, the imageis formed apart farther than the ocular fundus Er. Thus, as illustratedin FIG. 2B, the two split images cause a deviation between the right andleft straight-line images.

Thus, a table is provided so that a stop position of the prism unit 7 inthe direction of the optical axis with respect to a stop position of thefocus adjustment knob 25 is shifted corresponding to observation lightset by the observation light source selection switch 27.

In the alignment index unit 22, the visible LED 22 b as a visible indexlight source emits green light of 530 to 580 nm and has excellentvisibility in observation by visible light. The infrared LED 22 c as aninfrared index light source emits near infrared light to the extent of700 nm and does not make the eye to be examined E without mydriasis feelglare while retaining visibility, so that miosis can be prevented.

FIG. 3 illustrates an optical path diagram when an alignment index isprojected by visible light using the visible LED 22 b. Visible lightentered from the incident portion of the light guide 22 a as an indexprojection unit travels inside in a straight line and a luminous fluxreflected on the reflection surface changes an angle to travel in astraight line. Thus, a luminescent spot is formed at an outgoingportion. The luminescent spot formed therein is formed slightly insidean anterior eye portion Ep of the eye to be examined E by the objectivelens 2. An alignment index image including the luminescent spot iscombined with an ocular fundus image and observed via the findereyepiece lens 21 in the case of mydriatic observation, namelyobservation by visible light. At this time, when the luminescent spot ofthe alignment index is present on both sides of the ocular fundus imageby observation, it is indicated that the optical axes of the funduscamera and the eye to be examined E are aligned. When the luminescentspot is distinctly displayed without blurring, it is indicated that anoperation distance between the fundus camera and the eye to be examinedE is matched.

FIG. 4 illustrates an optical path diagram when the observation lightsource is changed from visible light of the halogen lamp 1 to infraredlight of the infrared LED 10 without adjusting the position of theluminescent spot of the alignment index. In a state of observation byinfrared light, the movable mirror 16 is pulled upward and the opticalpath is changed on the image sensor 17 side. When the visible LED 22 bhaving a long wavelength is used, the length of the optical path islengthened and an index position to be finally formed is deviatedbackward more than that of the image sensor 17. Therefore, if theposition of the luminescent spot of the alignment index is not adjusted,an operation distance cannot correctly be matched.

FIG. 5 illustrates an optical path diagram when the light source ischanged from the visible LED 22 b to the infrared LED 22 c by adjustingthe position of the alignment index in the case as described above. Thelight guide 22 a is shifted by the alignment index drive motor 23 sothat the incident portion faces the infrared LED 22 c. At this time, theoutgoing portion of the light guide 22 a is set in a position on whichan image is formed on the image sensor 17 when the operation distance isappropriate on the wavelength of the infrared LED 22 c. In other words,the visible LED 22 b and the infrared LED 22 c are disposed side by sidein the direction of the optical axis and an interval thereof correspondsto a distance that each light can form an image on the image sensor 17when the operation distance is appropriate. By employing such theconfiguration, when the light guide 22 a is shifted, the facing LED ischanged. Thus, while changing a luminescent color, a position of aluminescent point, namely the luminescent spot of the alignment indexcan also be changed.

FIG. 6 illustrates a block circuit diagram. The entire operation of thefundus camera is controlled by a central processing unit (CPU) 31. Theobservation light source selection switch 27 selects observation byinfrared light and observation by visible light corresponding to anobservation mode to be desired by a subject. In the present exemplaryembodiment, the observation light source is directly selected by theobservation light source selection switch 27. However, if aphotographing mode is selected from non-mydriatic/mydriaticphotographing, infrared light/visible light is selected by theobservation light source in conjunction therewith.

The alignment index drive motor 23 and the alignment index positiondetection unit 24 are connected to the CPU 31, so that the alignmentindex can be shifted to a desired position and the position can bedetected. A change between the visible LED 22 b and the infrared LED 22c is also controlled by the CPU 31, and the visible LED 22 b and theinfrared LED 22 c can be turned ON and OFF at a desired time.

FIG. 7 is a flowchart illustrating an operation executed by the CPU 31for changing a color and a position of an alignment index. In step S1,the operation is started. In step S2, a state of the observation lightsource selection switch 27 is checked. If visible light is selected (YESin step S2), the processing proceeds to step S3. If infrared light isselected (NO in step S2), the processing proceeds to step S4.

In step S3, a state of an alignment index is checked by the alignmentindex position detection unit 24. When it is in the state of infraredlight (YES in step S3), the processing proceeds to step S5. When it isin the state of visible light (NO in step S3), the processing proceedsto step S6. In step S5, the light guide 22 a is shifted by the alignmentindex drive motor 23, and the position of the alignment index is shiftedto the visible LED 22 b. In step S6, the visible LED 22 b for projectingthe alignment index is turned on. In step S7, a series of sequencesends.

In step S4, the state of the alignment index is checked by the alignmentindex position detection unit 24. When it is in the state of visiblelight (YES in step S4), the processing proceeds to step S8. When it isin the state of infrared light (NO in step S4), the processing proceedsto step S9. In step S8, the light guide 22 a is shifted by the alignmentindex drive motor 23, and the position of the alignment index is shiftedto the infrared LED 22 c. In step S9, the infrared LED 22 c forprojecting the alignment index is turned on. In step S7, a series ofsequences ends.

In the present exemplary embodiment, the alignment index is generatedusing the light guide 22 a. If an optical fiber or other light-guidingmembers is used, a similar effect can be obtained.

FIG. 8 illustrates a block diagram of a fundus camera according to asecond exemplary embodiment. The same reference numeral as that in FIG.1 in the first exemplary embodiment indicates the same member.

Instead of the visible LED 22 b and the infrared LED 22 c of thealignment index unit 22, a two-color LED 22 d is disposed which isintegrated with the light guide 22 a and shifted.

This configuration allows the two-color LED 22 d to selectively emitlight having two different wavelengths. Thus, a change in positionsbetween the visible LED 22 b and the infrared LED 22 c becomesunnecessary. An optical path length due to a difference in colors can beadjusted by shifting the two-color LED 22 d and the light guide 22 a.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications, equivalent structures, and functions.

This application claims priority from Japanese Patent Application No.2009-124348 filed May 22, 2009, which is hereby incorporated byreference herein in its entirety.

1. An ocular fundus observation apparatus comprising: an illuminationoptical system configured to illuminate an ocular fundus of an eye to beexamined; an observation photographing optical system configured toobserve and photograph the ocular fundus illuminated by the illuminationoptical system; an alignment index unit which is configured to projectan alignment index on an anterior eye portion of the eye to be examinedin order to adjust a position relation between the observationphotographing optical system and the eye to be examined, and is disposedto cause an image of a luminescent spot of the alignment index to beformed when an alignment is aligned with the anterior eye portion byshifting the observation photographing optical system; an infrared indexlight source configured to emit near infrared light and a visible indexlight source configured to emit visible light which are provided on thealignment index unit; an index light source change unit configured tochange these index light sources; an index projection unit configured tocause the index light source to emit light; and a shift control unitconfigured to control a position of the index projection unit in adirection of an optical axis, wherein a position of the luminescent spotof the index projection unit is changed by the shift control unitaccording to selection of the index light source of the index lightsource change unit.
 2. The ocular fundus observation apparatus accordingto claim 1, further comprising an observation light source selectionunit which can select an observation light source from near infraredlight and visible light, wherein the index light source change unitoperates in conjunction with the observation light source selectionunit.
 3. The ocular fundus observation apparatus according to claim 1,wherein the index projection unit uses a light guide.
 4. The ocularfundus observation apparatus according to claim 1, wherein the indexprojection unit uses an optical fiber.
 5. The ocular fundus observationapparatus according to claim 1, wherein an incident portion of the indexprojection unit is directed in a direction orthogonal to the opticalaxis, the infrared index light source and the visible index light sourceare disposed side by side in a direction of the optical axis, and theindex projection unit is shifted on either side of the index lightsources by the shift control unit.